Gravity (GRVY) had the highest return in January 2017 by a small-cap US stock, returning 78.3%.

ASSET	MONTH	% RETURN
Gravity (GRVY)	January 2017	78.34%
Taseko Mines (TGB)	January 2017	70.93%
Star Bulk Carriers (SBLK)	January 2017	65.84%
Semler Scientific (SMLR)	January 2017	65.56%
Viridian Therapeutics (VRDN)	January 2017	64.98%
Assembly Biosciences (ASMB)	January 2017	54.69%
Savara (SVRA)	January 2017	50.17%
American Battery Technology Company Common Stock (ABAT)	January 2017	47.72%
Ur Energy (URG)	January 2017	44.98%
United States Antimony (UAMY)	January 2017	44.81%
Aurinia Pharmaceuticals (AUPH)	January 2017	43.93%
Northern Dynasty Minerals (NAK)	January 2017	41.46%
Ichor (ICHR)	January 2017	40.11%
Astrana Health (ASTH)	January 2017	36.67%
Americas Silver (USAS)	January 2017	35.48%
Dorian LPG (LPG)	January 2017	35.45%
McEwen Mining (MUX)	January 2017	32.32%
North American Construction (NOA)	January 2017	31.64%
Larimar Therapeutics (LRMR)	January 2017	30.34%
Applied Opt (AAOI)	January 2017	29.73%
Metalla Royalty & Streaming (MTA)	January 2017	29.67%
Kornit Digital (KRNT)	January 2017	29.18%
Ultra Clean (UCTT)	January 2017	29.18%
Perion Network (PERI)	January 2017	28.28%
Mesabi Trust (MSB)	January 2017	28.11%

Small-cap stocks are treated as having a market cap between $300M and $2B.